﻿using System;
using System.IO;

namespace SanlieHash.GuoMi
{
    //https://gitee.com/mirrors/libtomcrypt/blob/develop/src/ciphers/sm4.c
    public class SM4
    {
        internal static readonly byte[] sbox = new byte[256]
        {
            0xd6, 0x90, 0xe9, 0xfe, 0xcc, 0xe1, 0x3d, 0xb7,0x16, 0xb6, 0x14, 0xc2, 0x28, 0xfb, 0x2c, 0x05,
            0x2b, 0x67, 0x9a, 0x76, 0x2a, 0xbe, 0x04, 0xc3,0xaa, 0x44, 0x13, 0x26, 0x49, 0x86, 0x06, 0x99,
            0x9c, 0x42, 0x50, 0xf4, 0x91, 0xef, 0x98, 0x7a,0x33, 0x54, 0x0b, 0x43, 0xed, 0xcf, 0xac, 0x62,
            0xe4, 0xb3, 0x1c, 0xa9, 0xc9, 0x08, 0xe8, 0x95,0x80, 0xdf, 0x94, 0xfa, 0x75, 0x8f, 0x3f, 0xa6,
            0x47, 0x07, 0xa7, 0xfc, 0xf3, 0x73, 0x17, 0xba,0x83, 0x59, 0x3c, 0x19, 0xe6, 0x85, 0x4f, 0xa8,
            0x68, 0x6b, 0x81, 0xb2, 0x71, 0x64, 0xda, 0x8b,0xf8, 0xeb, 0x0f, 0x4b, 0x70, 0x56, 0x9d, 0x35,
            0x1e, 0x24, 0x0e, 0x5e, 0x63, 0x58, 0xd1, 0xa2,0x25, 0x22, 0x7c, 0x3b, 0x01, 0x21, 0x78, 0x87,
            0xd4, 0x00, 0x46, 0x57, 0x9f, 0xd3, 0x27, 0x52,0x4c, 0x36, 0x02, 0xe7, 0xa0, 0xc4, 0xc8, 0x9e,
            0xea, 0xbf, 0x8a, 0xd2, 0x40, 0xc7, 0x38, 0xb5,0xa3, 0xf7, 0xf2, 0xce, 0xf9, 0x61, 0x15, 0xa1,
            0xe0, 0xae, 0x5d, 0xa4, 0x9b, 0x34, 0x1a, 0x55,0xad, 0x93, 0x32, 0x30, 0xf5, 0x8c, 0xb1, 0xe3,
            0x1d, 0xf6, 0xe2, 0x2e, 0x82, 0x66, 0xca, 0x60,0xc0, 0x29, 0x23, 0xab, 0x0d, 0x53, 0x4e, 0x6f,
            0xd5, 0xdb, 0x37, 0x45, 0xde, 0xfd, 0x8e, 0x2f,0x03, 0xff, 0x6a, 0x72, 0x6d, 0x6c, 0x5b, 0x51,
            0x8d, 0x1b, 0xaf, 0x92, 0xbb, 0xdd, 0xbc, 0x7f,0x11, 0xd9, 0x5c, 0x41, 0x1f, 0x10, 0x5a, 0xd8,
            0x0a, 0xc1, 0x31, 0x88, 0xa5, 0xcd, 0x7b, 0xbd,0x2d, 0x74, 0xd0, 0x12, 0xb8, 0xe5, 0xb4, 0xb0,
            0x89, 0x69, 0x97, 0x4a, 0x0c, 0x96, 0x77, 0x7e,0x65, 0xb9, 0xf1, 0x09, 0xc5, 0x6e, 0xc6, 0x84,
            0x18, 0xf0, 0x7d, 0xec, 0x3a, 0xdc, 0x4d, 0x20,0x79, 0xee, 0x5f, 0x3e, 0xd7, 0xcb, 0x39, 0x48,
        };
        internal static readonly uint[] sm4_FK = { 0xa3b1bac6, 0x56aa3350, 0x677d9197, 0xb27022dc };
        internal static readonly uint[] sm4_CK = {
            0x00070e15, 0x1c232a31, 0x383f464d, 0x545b6269,
            0x70777e85, 0x8c939aa1, 0xa8afb6bd, 0xc4cbd2d9,
            0xe0e7eef5, 0xfc030a11, 0x181f262d, 0x343b4249,
            0x50575e65, 0x6c737a81, 0x888f969d, 0xa4abb2b9,
            0xc0c7ced5, 0xdce3eaf1, 0xf8ff060d, 0x141b2229,
            0x30373e45, 0x4c535a61, 0x686f767d, 0x848b9299,
            0xa0a7aeb5, 0xbcc3cad1, 0xd8dfe6ed, 0xf4fb0209,
            0x10171e25, 0x2c333a41, 0x484f565d, 0x646b7279,
        };
        internal static uint getsbox(uint a)
        {
            uint B = 0;
            for (int i = 0; i < 4; i++,a>>=8) B |= (uint)(sbox[a & 0xff] << i * 8);
            return B;
        }
        internal static uint linearTransform(uint B)
        {
            return B ^ Helper.ROLT(B, 2) ^ Helper.ROLT(B, 10) ^ Helper.ROLT(B, 18) ^ Helper.ROLT(B, 24);
        }

        internal static uint compositeTransform(uint X)
        {
            return linearTransform(getsbox(X));
        }

        internal static uint linearTransform2(uint B)
        {
            return B ^ Helper.ROLT(B, 13) ^ Helper.ROLT(B, 23);
        }

        internal static uint compositeTransform2(uint X)
        {
            // 非线性变换τ，使用S盒进行处理
            // 线性变换L2
            return linearTransform2(getsbox(X));
        }

        internal static void _setRK(ref SM4_CTX ctx, bool reverse)
        {
            int i = 0;
            // K初始化，计算K的前4个元素
            ctx.K[0] = Helper.byte2uint(ctx.key, 0) ^ sm4_FK[0];
            ctx.K[1] = Helper.byte2uint(ctx.key, 4) ^ sm4_FK[1];
            ctx.K[2] = Helper.byte2uint(ctx.key, 8) ^ sm4_FK[2];
            ctx.K[3] = Helper.byte2uint(ctx.key, 12) ^ sm4_FK[3];

            // 循环32轮，计算出轮密钥
            for (i = 0; i < 32; i++) ctx.rk[reverse?31-i:i] = ctx.K[(i + 4)] = ctx.K[i] ^ compositeTransform2(ctx.K[i + 1] ^ ctx.K[i + 2] ^ ctx.K[i + 3] ^ sm4_CK[i]);
        }
        internal static void setRK(ref SM4_CTX ctx)
        {
            _setRK(ref ctx, false);
        }
        internal static void setRK_reverse(ref SM4_CTX ctx)
        {
            _setRK(ref ctx, true);
        }
        internal static void iterate32(ref SM4_CTX ctx)
        {
            // 中间变量，大小36个字
            ctx.K[0] = ctx.block[0];
            ctx.K[1] = ctx.block[1];
            ctx.K[2] = ctx.block[2];
            ctx.K[3] = ctx.block[3];

            // 32次迭代运算
            // 计算 4-35位置上的X元素
            for (var i = 0; i < 32; i++)  ctx.K[i + 4] = ctx.K[i] ^ compositeTransform(ctx.K[i + 1] ^ ctx.K[i + 2] ^ ctx.K[i + 3] ^ ctx.rk[i]);

            ctx.Rlt[0] = ctx.K[35];
            ctx.Rlt[1] = ctx.K[34];
            ctx.Rlt[2] = ctx.K[33];
            ctx.Rlt[3] = ctx.K[32];
        }
        internal static void done_oneblock(ref SM4_CTX ctx)
        {
            for (var i = 0; i < 16; i++) ctx.Rlt_bytes[i] = (byte)(ctx.Rlt[i >> 2] >> ((3 - i % 4) << 3));
        }

        internal SM4_CTX ctx;
        public SM4()
        {
            ctx= new SM4_CTX();
        }
        /// <summary>
        /// 16-bytes key
        /// </summary>
        /// <param name="key"></param>
        public void SetKey(byte[] key)
        {
            ctx.key = key;
        }

        public void New()
        {
            for (var i = 0; i < 16; i++) ctx.Rlt_bytes[i] = 0;
        }

        public byte[] EncryptOne(byte[] data)
        {
            ctx.block[0] = Helper.byte2uint(data, 0);
            ctx.block[1] = Helper.byte2uint(data, 4);
            ctx.block[2] = Helper.byte2uint(data, 8);
            ctx.block[3] = Helper.byte2uint(data, 12);
            setRK(ref ctx);
            iterate32(ref ctx);
            done_oneblock(ref ctx);
            return ctx.Rlt_bytes;
        }
        public byte[] DecryptOne(byte[] data)
        {
            ctx.block[0] = Helper.byte2uint(data, 0);
            ctx.block[1] = Helper.byte2uint(data, 4);
            ctx.block[2] = Helper.byte2uint(data, 8);
            ctx.block[3] = Helper.byte2uint(data, 12);
            setRK_reverse(ref ctx);
            iterate32(ref ctx);
            done_oneblock(ref ctx);
            return ctx.Rlt_bytes;
        }

        public byte[] Encrypt(byte[] data)
        {
            var len = data.Length + 4;
            if (len % 16 == 0) len -= 16;
            else if (len %16 <4) len -= len % 16 + 16;
            else len -= len % 16;

            var key = new byte[16];
            Array.Copy(ctx.key, key, 16);
            using (var mem = new MemoryStream())
            {
                for (int i = 0; i < len; i += 16)
                {
                    ctx.block[0] = Helper.byte2uint(data, i);
                    ctx.block[1] = Helper.byte2uint(data, i + 4);
                    ctx.block[2] = Helper.byte2uint(data, i + 8);
                    ctx.block[3] = Helper.byte2uint(data, i + 12);

                    for(var ikey = 0; ikey<16; ikey ++) ctx.key[ikey] ^= ctx.Rlt_bytes[ikey];
                    setRK(ref ctx);
                    iterate32(ref ctx);
                    done_oneblock(ref ctx);
                    mem.Write(ctx.Rlt_bytes, 0, 16);
                }

                byte[] raw = new byte[32];
                var ix = data.Length - len;
                if (len < data.Length) Array.Copy(data, len, raw, 0, ix);
                Array.Copy(Helper.uint2byte((uint)data.Length), 0, raw, ix, 4);

                ctx.block[0] = Helper.byte2uint(raw, 0);
                ctx.block[1] = Helper.byte2uint(raw, 4);
                ctx.block[2] = Helper.byte2uint(raw, 8);
                ctx.block[3] = Helper.byte2uint(raw, 12);

                for (var ikey = 0; ikey < 16; ikey++) ctx.key[ikey] ^= ctx.Rlt_bytes[ikey];
                setRK(ref ctx);
                iterate32(ref ctx);
                done_oneblock(ref ctx);
                mem.Write(ctx.Rlt_bytes, 0, 16);

                if (ix+ 4 > 16)
                {
                    ctx.block[0] = Helper.byte2uint(raw, 16);
                    ctx.block[1] = Helper.byte2uint(raw, 20);
                    ctx.block[2] = Helper.byte2uint(raw, 24);
                    ctx.block[3] = Helper.byte2uint(raw, 28);

                    for (var ikey = 0; ikey < 16; ikey++) ctx.key[ikey] ^= ctx.Rlt_bytes[ikey];
                    setRK(ref ctx);
                    iterate32(ref ctx);
                    done_oneblock(ref ctx);
                    mem.Write(ctx.Rlt_bytes, 0, 16);
                }


                Array.Copy(key, ctx.key, 16);
                return mem.ToArray();
            }
        }

        public byte[] Decrypt(byte[] data)
        {
            var key = new byte[16];
            Array.Copy(ctx.key, key, 16);
            var len = data.Length;

            using (var mem = new MemoryStream())
            {
                ctx.block[0] = Helper.byte2uint(data, 0);
                ctx.block[1] = Helper.byte2uint(data, 4);
                ctx.block[2] = Helper.byte2uint(data, 8);
                ctx.block[3] = Helper.byte2uint(data, 12);

                setRK_reverse(ref ctx);
                iterate32(ref ctx);
                done_oneblock(ref ctx);
                mem.Write(ctx.Rlt_bytes, 0, 16);


                for (var i = 16; i< len; i+=16)
                {
                    ctx.block[0] = Helper.byte2uint(data, i);
                    ctx.block[1] = Helper.byte2uint(data, i+4);
                    ctx.block[2] = Helper.byte2uint(data, i+8);
                    ctx.block[3] = Helper.byte2uint(data, i+12);

                    for (var ikey = 0; ikey < 16; ikey++) ctx.key[ikey] ^= data[i+ikey-16];
                    setRK_reverse(ref ctx);
                    iterate32(ref ctx);
                    done_oneblock(ref ctx);
                    mem.Write(ctx.Rlt_bytes, 0, 16);
                }
                len = 16 + 4;
                if (data.Length < len) len = 16;
                var raw = new byte[len];
                mem.Position =  mem.Length - len;
                mem.Read(raw,0, len);

                while (raw[len - 1] == 0) len--;
                var byteslength = Helper.byte2uint(raw, len - 4);
                mem.SetLength(byteslength);

                Array.Copy(key, ctx.key, 16);
                return mem.ToArray();
            }
        }
    }
}
